Organic phosphates



Patented May 1", woo

UNITED STATES PATENT OFFICE A 2,117,2ss onomc PHOSPHATES Shailer L.Bass, Midland, Mich., assignor to The Dow Chemical Company, Midland,Mich., a corporation of Michigan No Drawing. Application August 5, 1935,Serial No. 34,724

Claims.

This invention concerns certain new organic phosphates and a method ofmaking the same. Such new phosphates are in most instances water-whiteliquids which are exceptionally stable against hydrolysis by water,acids, and bases, and against decomposition by heat. They are useful asplasticizers for cellulose esters, cellulose ethers, and syntheticresins, being substantially non-flammable, so that they decrease theflammability of films and plastic masses in which 'they areincorporated.

In my copending application, Serial No. 744,913, filed September 21,1934, and issued March 17, 1936 as United States Patent 2,033,916, Ihave described and claimed certain triaryl phosphates having the generalformula wherein R and R represent aromatic groups. The presentapplication, which is a continuationin-part of said co-pendingapplication, deals particularly with mixed triaryl esters of phosphoricacid having the above general formula wherein R represents a cresylgroup and R represents either an orthochlorophenyl or a cresyl group.This invention, then, consists in the new compounds having the formulawherein R is a cresyl or an orthochlorophenyl group, together with themethod of making the same hereinafter fully described and particularlypointed out in the claims.

The herein described new organic phosphates, having the above generalformula, are prepared by reacting a phosphorus oxyhalide successivelywith orthochiorophenol and a cresol, or alkali metal salts of saidphenols. The order in which the different phenolic compounds are reactedis generally not important. For example, a phosphorus oxyhalide mayfirst be reacted with sufficient orthochlorophenol to form anorthochlorophenyl phosphoric acid dihalide or a di-orthosired, and theresultant acid halide may there after be reacted with one or more of theisomeric cresols to form the desired mixed trlaryl phosphate product.Also, the triaryl phosphate may be prepared by reactingorthochlorophenol with a monoor (ii-cresyl phosphoric acid halide, e.g., orthocresyl phosphoric acid dichloride, dimetacresyl phosphoric acidbromide, etc.

Each of the reactions just mentioned is carried out by heating a mixtureof the reactants to a reaction temperature, preferably in the presenceof a catalyst, such as metallic calcium, magnesium, or aluminum, or achloride of magnesium, aluminum, or iron, etc. The temperature to whichthe mixture must be heated in order to obtain rapid reaction is, ofcourse, dependent upon the particular reactants employed, the relativeproportions of the reactants, the presence or absence of a catalyst,etc. Since, however, the reaction is accompanied by an evolution of hy--drogen halide, it is suflicient merely to heat the mixture to atemperature at which hydrogen halide gas is evolved. The reactions arepreferably carried out at the lowest convenient reaction temperature,usually below 200 (2., since at higher temperatures by-product formationmay occur to an objectionable extent.

In preparing a mixed organic phosphate of the present class from aphosphorus oxyhalide and the appropriate phenolic compounds, theintermediate aryl phosphoric acid halide products may be separated assuch, e. g., by fractional distillation, prior to carrying out thesuccessive reactions, although it is more convenient, after formation ofsuch intermediate acid halide by reaction of phosphorus oxyhalide andone of the phenols merely to add the desired quantity oi the otherphenol to the mixture and to continue the reaction to form the triarylphosphate. The steps involved in separating the intermediate acid halideare thereby eliminated. After the reactions for the formation of thetriaryl phosphate are completed, the hot reaction mixture is preferablyblown with air to remove hydrogen halide and other volatile impuritiesand then fractionally distilled to separate the triaryl phosphateproduct.

The following equations for the successive formation of (1) anorthocresvl phosphoric acid dihalide, and (2) anorthocresyi-di-orthochlorophenyl phosphate illustrate the type ofreactions involved in preparing my new mixed triaryl phosphates by theabove-described procedure:

Example 1 A mixture of 432 grams (4.0 mols) of orthocresol and 1227grams (8.0 mols) of phosphorus oxychloride was heated at approximatelyC. for about 1 hour, until hydrogen chloride was no longer evolved. Then1.0 gram (.0105 moi.) of anhydrous magnesium chloride was added and themixture was heated, with stirring, at 108 C. for an additional 5.3hours, until the evolution of hydrogen chloride had again ceased.Orthocresyi phosphoric acid dichloride was separated from the reactedmixture by fractional distillation. It was obtained as a practicallyodorless, waterwhite, liquid boiling at approximately 135-6 C. under 19millimeters pressure and having the speciflc gravity 1.363 at 20/4 C.385.5 grams (3.0 mols) of orthochlorophenol, 337.5 grams (1.5 mols) ofthe orthocresyl phosphoric acid dichloride, and 10 grams (.105 moi.) ofmagnesium chloride were mixed and heated with stirring at temperaturesgradually increasing from 107 to 150 C. for 5.9 hours. Air was bubbledthrough the reacted mixture to remove dissolved hydrogen chloride andvolatile organic impurities, after which it was dissolved in 600 gramsof dichlorobenzene. The resultant solution was washed successively witha dilute aqueous hydrochloric acid solution, a dilute aqueous sodiumhydroxide solution, and water, and dried over anhydrous calciumchloride. It was then fractionally distilled under vacuum, whereby 493.2grams (1.2 mols) of substantially pure orthocresyl-di-orthochlorophenylphosphate was obtained. This product is-an odorless, water-white, liquidboiling at 268- 270 C. at 15 millimeters pressure, having a specificgravity of 1.336 at 25/4 C., the formula being;

Q I CH1 Example 2 A mixture of 6 grams (.063 mol.) of magnesiumchloride, 122.7 grams (.5 mol.) of orthochlorophenyl phosphoric aciddichloride, and 108.1 grams (1.0 mol.) of orthocresol was heated withstirring at temperatures gradually increasing from 100 to 150 C. for3.75 hours, at which time the quantity of hydrogen chloride gas evolvedindicated that approximately 97.0 per cent of the orthocresol had beenreacted. The reacted mixture was blown with air and then dissolved in200 grams of orthodichlorobenzene. The resultant solution was washedsuccessively Cl 01 c1 o1 i I with a dilute hydrochloric acid solution, adilute sodium hydroxide solution, and water, and dried over anhydrouscalcium chloride. It was then fractionally distilled under vacuum,whereby 161.2 grams (.41 mol.) of substantially purediorthocresyl-orthochlorophenyl phosphate was obtained as a viscous,light yellow, oily liquid, boiling at approximately 272-273 C. at 7millimeters pressure and having the specific gravity 1.262 at 25/4 C.The 'product has the formula;

Example 3 A mixture of 368 grams (1.5 mols) of orthochlorophenylphosphoric acid dichloride, 324 grams (3.0 mols) of metacresol, and 7.1grams (.0745 moi.) of magnesium chloride was heated with stirring attemperatures gradually increasing from 90 to'100 C. for 1.5 hours. Atthe end of this time the triaryl phosphate product was then separated asin Example 1. There was obtained 433.0 grams (1.12 mols) ofsubstantially pure di-metacresyl-orthochlorophenyi phosphate as anodorless, water-white liquid boiling at 279- 280 C. at 11-12 millimeterspressure and having the specific gravity 1.252 at 25/4 C. The prodnothas the formula;

Example 4 A mixture of 368 grams (1.5 mols) of orthochlorophenylphosphoric acid dichloride, 324 grams (3.0 mols) of paracresol, and 7.1grams (.0745 moi.) of magnesium chloride was heated with stirring attemperatures gradually increasing from to C. for 2.5 hours. The triaryiphosphate product was separated from the reacted mixture as inExample 1. There was obtained 403 grams (1.08 mols) ofdi-paracresylorthochloro-phenyl phosphate having a boiling point ofapproximately 282-284= C. at 9-10 millimeters pressure, a meltingpoint'of approximately 41 C., and a specific gravity of 1.227 at 60 C.The product was purified by recrystallization from 90 per cent methylalcohol, whereby it was obtained in the form of short prismatic crystalsmelting at 52-53 C. It has the formula:

Example A quantity of 324 grams (3.0 mols) of a technical mixture ofmeta and para cresol, 460.2 grams (3.0 mols) of phosphorus oxychloride,and 5.7 ams (0.06 mol.) of anhydrous magnesium chloride was heated atapproximately 70 C. for about 4 hours, i. e. until hydrogen chloride wasno longer evolved. 768 grams (6.0 mols) of orthochlorophenol was thenadded and the reaction completed by heating the mixture with stirring attemperatures gradually increasing from 70 to 150 C. for 6 hours. Thetriaryl phosphate product was then separated as in Example 1. There wasobtained 1050.0 grams (2.55 mols) of isomericmono-cresyl-di-orthochlorophenyl phosphates as an odorless, water-whiteliquid boiling at 293-298 C. at 9 millimeters pressure and having thespecific gravity 1.308 at 25/25 C.

In similar manner phosphorus oxychloride may successively be reactedwith:--(1) metacresol, paracresol, and orthochlorophenol to producemetacresyl-paracresyl-orthochloro-phenyl phosphate; (2) orthocresol,paracresol, and orthochlorophenol to produceorthocresyl-paracresylorthochlorophenyl phosphate, etc.

Although I prefer to employ phosphorus oxychloride as a reactant inpreparing the herein described new organic phosphates, phoshorusoxybromide or phosphorus oxyiodide may be used instead.

Other modes of applying the principle of my invention may be employedinstead of those explained, change being made as regards the method orcompounds herein disclosed, provided the steps or compounds stated byany of the fol lowing claims or the equivalent of such stated steps orcompounds be employed. I

I therefore particularly point out and distinctly claim as my invention:

1. In a method of making a triaryl phosphate having the general formulaC] CH: W

wherein R represents a member of the class consisting of the cresyl andorthochlorophenyl groups, the step which consists in heating anorthochlorophenyl phosphoric 'acid halide to a reaction temperature witha cresol.

3. In a method of making a triaryl phosphate having the general formula0 0-1: wherein R represents-a member 01' the class consisting of thecresyl and orthochlorophenyl groups, the steps which consist in reactinga phosphorus oxyhalide with a cresol to form a corresponding cresyl'phosphoric acid halide, and thereafter reacting the latter withorthochlorophenol.

4. In a method of making a triaryl phosphate having the general formulawherein R represents a member of the class consisting of the cresyl andorthochlorophenyl groups, the steps which consist in reacting phosphorusoxychloride with a cresol to form a corresponding cresyl phosphoric acidchloride and thereafter reacting the latter with orthochlorophenol.

5. In a method of making a triaryl phosphate having the general formulawherein R represents a member of the class consisting of the cresyl andorthochlorophenyi groups, the step which consists in reacting a c'resylphosphoric acid halide with orthochlorophenol.

6. In a method of making a triaryl phosphate having the general formulawherein R represents a member of the class consisting of the cresyl andorthochlorophenyl wherein R represents a member of the class consistingof the cresyl and orthochlorophenyl groups, the steps which consist inreacting a phosphorus omrhalide with a mixture of the isomeric cresolsto form corresponding cresyl phosphoric acid halides, and thereafterreacting the latter with orthochlorophenol.

9. In a method of making orthocresyl-cli-orthochlorophenyl phosphate,the steps which consist in heating phosphorus oxychioride to a reactiontemperature with approximately its molecular equivalent of orthocresolto form orthocresyl phosphoric acid dichloride, and thereafter heatingthe latter to a reaction temperature with sufiicient orthochlorophenolto form the desired mixed triaryl phosphate product.

10. In a method of making di-orthocresylorthochlorophenyi phosphate, thestep which consists in heating orthochlorophenyl phosphoric aciddichloride to a reaction temperature with sumcient orthocresol to formthe desired mixed triaryl phosphate product.

11. In a method of making a cresyl-di-orthochlorophenyl phosphateproduct, the step which consists in heating a mixture of meta and paracresyl phosphoric acid dichlorides to a reaction temperature withsufiicient orthochlorophenol to form the desired mixed triarylphosphate.

12. A triaryl phosphate having the general formula wherein R representsa member of the class consisting of the cresyl and orthochloz'ophenylgroups.

13. Orthocresyl-di-orthochlorophenyl phosphate, a viscous liquid boilingat approximately 270 C. at 15 millimeters pressure. having the specificgravity 1.338 at /4 C., and having the formula 14. Di orthocresylorthochlorophenyl phosphate, a viscous liquid boiling at approximately273 C. at 7, millimeters pressure, having the specific gravity 1.262 at25F? 0., and having the formula (Ill CH:

